Treadwellphysa rizzoae, Molina-Acevedo, 2019

Molina-Acevedo, Isabel C., 2019, Redescription of two species previously regarded as Marphysa de Quatrefagesı 1865 ı with the description of new species of Treadwellphysa Molina-Acevedo and Carrera-Parraı 2017, Journal of Natural History 53 (9), pp. 517-540 : 530-534

Treadwellphysa rizzoae sp. nov.

( Figures 5 – 7 )

Material examined

Type material. Holotype ECOSUR204 ; Tiririca Bay, Itacaré, Bahia, Brazil; - 14.287°S - 38.985°W; 10 December 2012; on rock; 0 m; coll. E. da C. Guerreiro Couto . Paratypes ECOSUR205 (1), UERJ 6955 (1); Prainha, Itacaré, Bahia, Brazil; - 14.307°S - 38.988°W; 12 December 2012; on rock; 0 m; coll . E. da C. Guerreiro Couto.

Description

Holotype complete, with 210 chaetigers, L10 = 10.3 mm, W10 = 4 mm, TL = 100 mm. Anterior region of body with convex dorsum and flat ventrum, without groove; body depressed from chaetiger 9, widest at chaetiger 44, tapering after chaetiger 72.

Prostomium bilobed, 2 mm long, 2.5 mm wide; lobes frontally rounded; median sulcus shallow ( Figure 5 (a – c)), ventral sulcus deep ( Figure 5 (b)). Prostomial appendages in a semicircle, median antenna isolated by a gap. Left palp broken, right palp reaching first peristomial ring; left lateral antenna broken, right lateral antenna reaching first chaetiger; median antenna reaching second chaetiger. Palpophores and ceratophores ring-shaped, short, thick; palpostyles and ceratostyles tapering, slender, without articulation. Eyes reniform, brown, between palps and lateral antennae.

Peristomium larger than prostomium (2.3 mm long, 3.5 mm wide), first ring 2 times longer than second ring, separation between rings distinct on all sides ( Figure 5 (a – c)). Ventral lip with a slight central depression ( Figure 5 (b)).

Maxillary apparatus with MF = 1+1, 3+4, 4+0, 4+6, 1+1 ( Figure 5 (d)). Maxillary carriers 2.4 times shorter than length of MI. MI forceps-like; closing system 3.4 times shorter than length of MI; ligament between MI and MII sclerotised ( Figure 5 (d,e)). MII with recurved teeth; cavity opening oval, 3.4 times shorter than length of MII; ligament between MII and MIII and right MIV, sclerotised ( Figure 5 (d,e)). MIII short; with blunt teeth; with irregular attachment lamella, situated in centre of the right edge of maxilla, slightly sclerotised ( Figure 5 (d,e)). Left MIV with two larger lateral teeth; attachment lamella semicircular, slender, better developed in central portion, situated along anterior edge of maxilla ( Figure 5 (d,e)). Right MIV with two larger lateral teeth; attachment lamella semicircular, slender, better developed in central portion and on right side, situated along of anterior edge of maxilla ( Figure 5 (d)). MV square, with a short, rounded tooth ( Figure 5 (d,e)). Mandibles dark ( Figure 5 (f)); calcareous cutting plates broken, cutting plates amber, oval, with up to nine growth rings.

Branchiae pectinate with up to four filaments, in chaetigers 29 to 192L – 193R ( Figure 6 (c – f)). One filament along chaetigers 29L to 32L; two filaments along chaetigers 33L to 47L; three filaments along chaetigers 48L to 60L; four filaments along chaetigers 61L to 86L; three filaments along chaetigers 87L to 113L; two filaments along chaetigers 114L to 139L; one filament along chaetigers 140L to 192L. Branchial filaments longer than dorsal cirri ( Figure 6 (c – f)).

First four parapodia smaller; best developed in chaetigers 9 – 81, following ones becoming gradually smaller. Notopodial cirri conical, longer than ventral cirri in first 14 chaetigers, in chaetigers 15 to 30 of similar sizes, following ones gradually decreasing in size, shorter than ventral cirri ( Figure 6 (a – f)). Prechaetal lobes short, as a transverse fold in all chaetigers ( Figure 6 (a – f)). Chaetal lobes in chaetigers 1 – 40 rounded, slightly shorter than postchaetal lobes, with aciculae emerging dorsal to midline; from chaetiger 41 triangular, longer than other lobes, with acicula emerging in midline ( Figure 6 (a – f)). Postchaetal lobes poorly developed in chaetigers 1 – 71, rounded; progressively decreasing in size from chaetigers 21 to 71; following ones inconspicuous ( Figure 6 (a – f)). Ventral cirri in chaetigers 1 – 5 conical; in chaetigers 6 – 85 with a swollen base as a transverse welt with a short digitiform tip; from chaetiger 86 digitiform, gradually decreasing in size ( Figure 6 (a – f)).

Aciculae blunt, reddish along most of its length, translucent on the distal tip ( Figure 6 (a – f)). First chaetiger with two aciculae, chaetiger 2 with three, chaetiger 3 with four, chaetigers 4 – 34 with three, chaetigers 35 – 90 with two, from chaetiger 91 with only one acicula.

Limbate chaetae of two lengths in the same chaetiger, longer in dorsal region of the parapodia, reduced in number in anterior chaetiger. Three types of pectinate chaetae; in anterior chaetigers, isodont narrow, with short and slender teeth, with 2 – 3 pectinate, with up to 17 – 18 teeth ( Figure 7 (a)); in median-posterior chaetigers, isodont wide, with short and slender teeth, with 6 – 7 pectinate, with up to 25 teeth ( Figure 7 (b)); in posterior chaetigers, anodont wide, with long and thick teeth, with 1 – 2 pectinate, with up to 14 – 15 teeth ( Figure 7 (c)). Compound spinifalciger and spiniger absent. Compound falcigers present in all chaetigers; in anterior region with blades of two lengths (longer 60 µm, Figure 7 (d,f), smaller 49 µm, Figure 7 (d,e)); distal tooth blunt and proximal triangular, of similar size, distal tooth directed slightly upward, proximal tooth directed laterally. In median-posterior chaetigers all blades of similar length, slightly shorter than longer blades of anterior chaetigers (56 µm, Figure 7 (g)); all with triangular teeth, distal tooth shorter than proximal, directed upward, proximal tooth directed laterally. Subacicular hooks bidentate, reddish along most of its length, translucent on the distal tip, starting from chaetiger 34, one per chaetiger, except for replacement; with triangular teeth, distal tooth smaller than proximal, directed upward, proximal tooth directed laterally ( Figure 7 (h,i)).

Pygidium with two pairs of anal cirri, without articulation; dorsal pair as long as last four chaetigers; ventral pair short, as long as last chaetiger.

Variations

Material examined with L10 = 4.7 – 10.3 mm and W10 = 3.1 – 4 mm. Paratypes incomplete with 49 and 84 chaetigers. Palps reaching first or second peristomial ring. Lateral antennae reaching second peristomial ring or second chaetiger. Median antenna reaching first or second chaetiger. The maxillary formula variations are MII 3 + 3 – 4, MIII 4 , MIV 4 + 6 – 7. The proportions of the maxillary apparatus vary as follows: maxillary carriers 2.4 – 2.75 times shorter than the length of the MI; the closing system 3.4 – 3.7 times shorter than the length of the MI; the cavity opening 3.4 – 4 times shorter than the length of the MII. Branchiae from chaetigers 29 – 31 to 18 chaetigers before pygidium. Maximum number of branchial filaments varied from two to four. Poorly developed postchaetal lobe present in first 47 – 71 chaetigers. Ventral cirri with a swollen base from chaetigers 5 to 125 chaetigers before pygidium. Start of subacicular hooks in chaetigers 32 – 34.

Distribution

Bahia, Brazil.

Etymology

This species is named in honour of my Brazilian colleague Alexandra E. Rizzo, in recognition of her valuable contributions to the taxonomic study of the polychaetes from Brazil and for donating these materials.

Remarks

Treadwellphysa rizzoae sp. nov. has in common with T. languida , T. veracruzensis and T. villalobosi sp. nov. the presence of compound falcigers and the absence of the compound spinigers. However, T. languida and T. veracruzensis present compound spinifalcigers, while T. rizzoae sp. nov. and T. villalobosi sp. nov. lack spinifalcigers. Besides, in T. rizzoae sp. nov. postchaetal lobes are rounded and similar in size to chaetal lobes, whereas in T. languida postchaetal lobes are conical and longer than chaetal lobes. In T. rizzoae sp. nov. branchiae start in chaetigers 29 – 31, while in T. veracruzensis branchiae start in chaetigers 15 – 49, and in T. villalobosi sp. nov. they start in chaetigers 39 – 53. Moreover, T. rizzoae sp. nov. (holotype with 210 chaetigers) has subacicular hooks that are reddish along most of its length and translucent on the distal tip, and branchiae finish 18 chaetigers before the pygidium; whereas T. villalobosi sp. nov. (holotype with 417 chaetigers) has translucent subacicular hooks, and branchiae finish 41 chaetigers before the pygidium. Finally, in T. rizzoae sp. nov. the subacicular hooks start in chaetiger 32 – 34, while in T. villalobosi sp. nov. the hooks start in chaetiger 31 – 46.

Figures

Figure 5. Treadwellphysa rizzoae sp. nov. (a) Anterior end, dorsal view; (b) anterior end, ventral view; (c) anterior end, lateral view; (d) maxillary apparatus, dorsal view, arrows indicate the elevation in the base of MII; (e) left MI–V, lateral view, arrows indicate ligament between maxillae; (f) mandibles. a–b, d–f from holotype ECOSUR204; c from paratype ECOSUR205. Scale bars: a–b = 2.6 mm; c = 2 mm; d–f = 1 mm.

Figure 6. Treadwellphysa rizzoae sp. nov., holotype ECOSUR204. (a) Parapodium 3; (b) parapodium 6; (c) parapodium 34; (d) parapodium 90; (e) parapodium 144; (f) parapodium 210. Scale bars: a = 0.1 mm; b = 0.2 mm; c–e = 0.32 mm; f = 1.5 mm. All parapodia in anterior view.

Figure 7. Treadwellphysa rizzoae sp. nov. (a) Chaetiger 9, isodont pectinate narrow, with short and slender teeth; (b) chaetiger 163, isodont pectinate wide, with short and slender teeth; (c) chaetiger 163, anodont pectinate wide with long and thick teeth; (d) chaetiger 9, compound falcigers with long and short blade; (e) chaetiger 6, compound falciger with short blade; (f) chaetiger 9, compound falciger with long blade; (g) chaetiger 163, compound falciger in posterior region; (h) chaetiger 90, subacicular hook; (i) chaetiger 163, subacicular hook. b–c, e–i from holotype ECOSUR204; a, d from paratype ECOSUR205. Scale bars: a–b = 7.1 µm; c = 14.5; d, g = 13.8 µm; e–f = 10.5 µm; h = 36 µm; i = 14.3 µm. The number 1 indicates the compound falciger with long blade; 2 indicates the compound falciger with short blade.